Method for extracting copper from leach solutions at elevated temperatures

ABSTRACT

Copper is extracted from aqueous copper leach solutions wherein the leach solutions have a temperature of at least 30° C. The method comprises contacting the aqueous solution with an extraction reagent of the formula (I)  
                 
 
     wherein R is a linear or branched C 10-18  alkyl group and R 1  is H or CH 3 . These extraction reagents do not undergo any significant degradation normally encountered with the use of conventional reagents in leach solutions having temperatures equal to or greater than 30° C.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of copending provisional application Ser. No. 60/470,657 filed on May 15, 2003, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] Advances in leaching copper concentrates or high grade copper sulfide ores using either pressure leaching or leaching in stirred tanks with the assistance of ferric ion or bacteria results in leach solutions having a relatively high temperature. The temperatures of most leach liquors treated today is from about 15° C. to about 25° C. The leach solutions exiting pressure leach vessels or stirred tanks can be as high as 150° C. depending on the leaching technique. For several reasons, including the stability of the copper solvent extraction reagent, there are difficulties in treating leach solutions at these high temperatures via copper solvent extraction. As a result these leach solutions are cooled to not more than about 45 to 50° C. prior to entering the copper solvent extraction plant.

[0003] In a commercial copper solvent extraction (SX) plant that uses the elevated temperature leaching technology, the extraction molecule 5-nonylsalicylaldoxime has been used in admixture with 2,2,4-trimethyl-1,3-pentanedioldiisobutyrate, also known by the trade name TXIB. TXIB belongs to a class of compounds called equilibrium modifiers which are disclosed in U.S. Pat. Nos. 4,507,268 and 6,231,784, the entire contents of each of which is incorporated herein by reference. Modifiers alter the normal copper extraction ability of an extractant thereby allowing one to carefully select a blend of 5-nonylsalicylaldoxime and modifier that is optimum or near optimum for a particular copper solvent extraction application.

[0004] Of concern to operators of copper solvent extraction plants is the hydrolytic degradation of extractants such as 5-nonylsalicylaldoxime since degradation of the extractant represents both an additional cost and an operational problem. The additional cost arises because the reagent lost via degradation must be replaced.

[0005] The operational problem arises because the degradation of extractants such as 5-nonylsalicylaldoxime is at a higher rate than the degradation of the modifier so that over a period of time the ratio of 5-nonylsalicylaldoxime to modifier in the organic phase in the SX plant slowly decreases. As this ratio decreases the mixture of 5-nonylsalicylaldoxime to modifier will no longer be optimum for the particular copper solvent extraction plant. In order to maintain the mixture of 5-nonylsalicylaldoxime and TXIB at the optimum in the plant both of these compounds must be monitored using sophisticated analytical equipment and then the plant operators must calculate the amount of pure 5-nonylsalicylaldoxime which must be added on a regular basis along with the normal copper solvent reagent in order to maintain the proper blend of 5-nonylsalicylaldoxime to modifier in the plant organic.

[0006] Clearly then there exists a need for a copper extraction molecule that is more stable than 5-nonylsalicylaldoxime in order to reduce reagent loss by degradation and to reduce the number of sophisticated analyses that are required to maintain the proper ratio of copper extraction molecules to modifier.

BRIEF SUMMARY OF THE INVENTION

[0007] The present invention pertains to a method for extracting copper from an aqueous copper solution wherein the aqueous copper solution has a temperature of at least 30° C. The method comprises contacting the aqueous copper solution with an extraction reagent of the formula (I)

[0008] wherein R is a linear or branched C₁₀₋₁₈ alkyl group and R₁ is H or CH₃. The extraction reagents according to the invention undergo degradation at a significantly lower rate than normally encountered with the use of conventional reagents in leach solutions having temperatures equal to or greater than 30° C.

DETAILED DESCRIPTION OF THE INVENTION

[0009] The extractants according to the invention are compounds of the formula (I)

[0010] wherein R is a linear or branched C₁₀₋₁₈ alkyl group and R₁ is H or CH₃. Compounds of formula (I) wherein R₁ is H may be prepared according to methods described in U.S. Pat. No. 4,020,105 or 4,020,106 or by oximation of aldehydes prepared according to U.S. Pat. No. 4,085,146, the entire contents of each of which is incorporated herein by reference. Compounds of formula (I) wherein R₁ is CH₃ can be prepared according to the procedures disclosed in UK Patent 1,322,532. Preferred extractants include 2-hydroxy-5-decylacetophenone oxime, 2-hydroxy-5-dodecylacetophenone oxime, 2-hydroxy-5-pentadecylacetophenone oxime, 5-decylsalicylaldoxime, 5-dodecylsalicylaldoxime, and 5-pentadecylsalicylaldoxime and mixtures thereof.

[0011] The extractants according to the invention can be and typically are dissolved in a commercial hydrocarbon solvent such as CONOSOL® 170ES, ORFOM® SX 7, ORFOM® SX 12, ORFOM® SX 11, Shellsol 2046 and similar solvents at a concentration greater than about 0.25 M. The organic extractant may also contain an equilibrium modifier which can include an ester such as 2,2,4-trimethylpentane-1,3-diol diisobutyrate, di-n-butyl adipate, a ketone, an ether, or an alcohol such as tridecyl alcohol. The organic extractant may contain additional oxime extractants. The aqueous feed solution temperature range may be greater than or equal to 30° C., 35° C., or 40° C. The concentration of copper in the aqueous feed solution will typically vary from about 5 gpl Cu to about 50 gpl Cu, most preferably it will be greater than 10 gpl Cu. The leach liquor may result from pressure oxidation of a concentrate or a bio-oxidation process carried out on a concentrate.

[0012] The following examples are meant to illustrate but not to limit the invention.

EXAMPLE

[0013] A series of stability tests were carried out by continuously stirring an aqueous phase containing 30 gpl (grams per liter) Cu and 180 gpl sulfuric acid with an organic extractant phase at 45° C. Approximately 350 ml of the aqueous phase and 350 ml of the organic phase were placed in a standard 3-neck 1 liter round bottom glass flask fitted with an overhead stirrer motor, Teflon® paddle stirrer and a Friedrigs condenser. The flask was placed in a thermostated oil bath to control the temperature at 45° C. The agitator was set at 480 rpm. Samples of the organic were removed periodically and analyzed for copper max load and for oxime content.

[0014] In Test 1, the organic phase was 0.0463 M in 5-nonylsalicylaldoxime, 0.0425 M in 5-dodecylsalicyladoxime, and 0.104 M in di-n-butyl adipate dissolved in CONOSOL® 170ES. The results are summarized in Table 1. TABLE 1 Time 5-Nonylsalicylaldoxime 5-Dodecylsalicylaldoxime (Days) (m/l) (m/l) 0 0.0463 0.0425 56 0.0333 0.0362 84 0.0273 0.0328 112 0.0220 0.0292 139 0.0189 0.0266 168 0.0174 0.0260 196 0.0146 0.0233 224 0.0109 0.0189 252 0.0084 0.0154 260 0.0081 0.0149

[0015] Based on the data, 5-nonylsalicylaldoxime has a half life of approximately 115 days, significantly less than 5-dodecylsalicylaldoxime, which has a half life of 220 days under these test conditions.

[0016] In Test 2, the organic phase was 0.2640 M in 2-hydroxy-5-nonylacetophenone oxime (Ketoxime), 0.3091 M in 5-nonylsalicylaldoxime (C9 Aldox), and 0.0202 M 5-dodecylsalicylaldoxime (C12 Aldox) in CONOSOL® 170ES. The results are summarized in Table 2. TABLE 2 Time Ketoxime C9 Aldox C12 Aldox (Days) (m/l) (m/l) (m/l) 0 0.2640 0.3091 0.0202 28 0.2403 0.2253 0.0158 56 0.2243 0.1823 0.0134 84 0.2086 0.1522 0.0123 112 0.1947 0.1274 0.0113 140 0.1833 0.1130 0.0107 168 0.1709 0.1012 0.0098 196 0.1611 0.0928 0.0089 224 0.1529 0.0868 0.0081 252 0.1475 0.0829 0.0078

[0017] Based on the data, the half life of 5-nonylsalicylaldoxime was approximately 83 days while the half life of the 5-dodecylsalicylaldoxime was 170 days, significantly greater than that of the 5-nonylsalicylaldoxime. The 2-hydroxy-5-nonylacetophenone oxime was significantly more stable than the two aldoximes. It is estimated to have a half life greater than 330 days under these test conditions. 

What is claimed is:
 1. A method comprising extracting copper from an aqueous copper solution having a temperature of at least 30° C. by contacting the aqueous solution with an extraction reagent of the formula (I)

wherein R is a linear or branched C₁₀₋₁₈ alkyl group and R₁ is H or CH₃.
 2. The method of claim 1 wherein the extraction reagent is further comprised of a hydrocarbon diluent.
 3. The method of claim 1 wherein R is a linear or branched C₁₀₋₁₈ alkyl group and R₁ is H.
 4. The method of claim 1 wherein R is a linear or branched C₁₀₋₁₈ alkyl group and R₁ is CH₃.
 5. The method of claim 1 wherein the extraction reagent is selected from the group consisting of 2-hydroxy-5-decylacetophenone oxime, 2-hydroxy-5-dodecylacetophenone oxime, 2-hydroxy-5-pentadecylacetophenone oxime, 5-decylsalicylaldoxime, 5-dodecylsalicylaldoxime and 5-pentadecylsalicylaldoxime.
 6. The method of claim 5 wherein the extraction reagent is 5-dodecylsalicylaldoxime.
 7. The method of claim 5 wherein the extraction reagent is 2-hydroxy-5-dodecylacetophenone oxime.
 8. The method of claim 5 wherein the extraction reagent is 5-decylsalicylaldoxime.
 9. The method of claim 5 wherein the extraction reagent is 2-hydroxy-5-decylacetophenone oxime.
 10. The method of claim 5 wherein the extraction reagent is 2-hydroxy-5-pentadecylacetophenone oxime.
 11. The method of claim 5 wherein the extraction reagent is 5-pentadecylsalicylaldoxime.
 12. The method of claim 1 wherein the extraction reagent is further comprised of a modifier selected from the group consisting of an ester, a ketone, an ether and an alcohol.
 13. The method of claim 12 wherein the alcohol is tridecanol.
 14. The method of claim 12 wherein the ester is 2,2,4-trimethylpentane-1,3-diol diisobutyrate, di-n-butyl adipate.
 15. The method of claim 1 wherein the temperature is 35° C.
 16. A method comprising extracting copper from an aqueous copper solution having a temperature of at least 30° C. by contacting the aqueous solution with a composition comprising: (a) extraction reagent comprised of a compound of the formula (I)

wherein R is a dodecyl group and R₁ is H and (b) di-n-butyl adipate.
 17. A method comprising extracting copper from an aqueous copper solution having a temperature of at least 30° C. by contacting the aqueous solution with a composition comprising: (a) extraction reagent comprised of a compound of the formula (I)

wherein R is a nonyl group and R₁ is CH₃ and (b) di-n-butyl adipate.
 18. The method of claim 16 wherein the temperature is 35° C.
 19. The method of claim 17 wherein the temperature is 35° C. 